package com.yx.gifts.adapter;

import android.graphics.Rect;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * Created : Yx
 * Time : 2018/11/21 11:40
 * Describe :RecyclerView -  Item适配分割线、间距
 * 适当调调就可以得到想要的间距
 */
public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

    private int spanCount;//列数
    private int spacing;//间距,单位：px
    private boolean includeEdge;//是否包含边界：true代表有边界，false代表无边界

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view); // item position
        int column = position % spanCount; // item column
        if (includeEdge) {
            outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
            outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

            if (position < spanCount) { // top edge
                outRect.top = 0;
            }
            outRect.bottom = spacing / 2; // item bottom 去掉就默认等于中间间隔
        } else {
            outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
            outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
            if (position >= spanCount) {
                outRect.top = spacing; // item top
            }
        }
    }
}
